CRM 2011 Error - crm 2011 Object of type 'Microsoft.Xrm.Sdk.Entity' cannot be converted to type

Add .EnableProxyTypes(); to call service


        using (OrganizationServiceProxy serviceProxy = GetProxy())
        {
            serviceProxy.EnableProxyTypes();   
          IOrganizationService service =(IOrganizationService)serviceProxy;
            return service.Retrieve(entityName, id, columSet);   
     }